1992 Honda Accord Squeaky noises

I purchased a 1992 Honda accord with 240,000 miles on it. I took it to my mechanic to have the timing belt replaced since the previous owner had never had it done. I paid $580 for the job. Two weeks after the work being done, the car stalled while I was driving it and lost power. I had it towed back to my mechanic and he said it needed a belt (I don't recall what belt). He replaced that and now the car makes a loud squeaky noise when started. It used to go away once I drove the car but now the noise stays. I took it back to him and he says it could be the tensioner and wants to charge me another $350. I thought the tensioner should have been replaced when he did the timing belt job. What could the noise be? I am not trusting him now, I feel he is just trying to get more money out of me.